This invention relates generally to ignition systems for internal combustion engines. More particularly, this invention relates to laser ignition systems and features that optimize the optics and optical access included in a laser ignition system, for internal combustion engines.
For internal combustion engines, fuel is combusted with an oxidizer (usually air) in combustion chambers. The resulting high temperature and pressure gases expand and thereby apply forces to movable components of the engines, such as turbine blades to drive the turbine. Combustion can be intermittent (as for example, in automotive applications) or continuous (as for example, in gas turbines and jet engines).
In a conventional ignition apparatus for internal combustion engines, a high voltage is applied to an ignition plug that is fixed on a wall surface of the combustion chamber in order to ignite an air-fuel mixture by spark discharge. However, in an ignition apparatus of this kind, since the ignition plug is exposed directly to the combustion chamber, carbon attaches to the ignition plug to render the discharge of the ignition plug difficult. In addition, electrode erosion may be of concern in this type of configuration. Furthermore, due to a heat loss of the electrodes of the ignition plug, a torch or nucleus of flame generated by the discharge is cooled, and vanishes before reaching a flame. Additionally, since the ignition occurs on or very near the wall surface, a high fuel fraction close to the combustor wall often results due to the difficulties associated with burning fuel from the wall surface.
Engines that use combustible fuel such as, for example, gas turbine engines and other internal combustion engines include combustion areas such as, for example, combustors or cylinder and piston assemblies that facilitate the conversion of energy from combustion into mechanical energy. Fuel nozzles are used to introduce atomized fuel into the combustion areas. The atomized fuel is ignited by an igniter. Igniters may include, for example, electrical igniters that create a spark proximate to the atomized fuel, heating elements that introduce heat to the atomized fuel, and igniters that introduce a flame in the combustion area, such as laser igniters. In an attempt to enhance laser ignition of the fuel in the combustion chamber, optimizing the associated optics and optical access utilized during ignition is desired.
Accordingly, there is a need for a new and improved laser ignition system and method for internal combustion engines in which optimized optics and optical access are provided in an attempt to improving ignitability within the combustion region.